This invention relates in general to separation of receiver members from dielectric members in electrostatographic reproduction apparatus, and more particularly to a grounded conductive member of sharp edge configuration positioned at a predetermined location for facilitating receiver member separation.
In typical electrostatographic reproduction apparatus or the like, an electrostatic latent image on a dielectric member is developed with pigmented marking particles. A receiver member, such as a sheet of plain bond paper for example, is brought into registered contact with the developed marking particle image on the dielectric member, and the marking particle image is electrostatically transferred to the receiver member. Thereafter, the receiver member is separated from the dielectric member and transported to a downstream device where the marking particle image is fixed to the receiver member by heat and/or pressure.
The electrostatic forces effecting transfer of the marking particle developed image to the receiver member also cause the receiver member to adhere to the dielectric member. Accordingly, it is a common practice in such reproduction apparatus to provide a device for effecting positive separation of the receiver member from the dielectric member after transfer. Such devices may be of the electrical type or of the mechanical type (or some combination thereof).
Electrical type separation devices typically employ a high voltage AC corona charger to neutralize the electrostatic charge causing the receiver member to adhere to the dielectric member thus facilitating the desired separation. The use of such chargers, however, requires that sufficient space be available within the reproduction apparatus. Moreover, they significantly increase the power demand, EMI noise and ozone generation of the apparatus. Mechanical type separation devices utilize for example relatively small diameter rollers in the dielectric member travel path or strippers in contact with the dielectric member. To effect separation with relatively small diameter rollers, the abrupt change in direction of the dielectric member moving about its travel path and the beam strength of the receiver member is relied upon to cause the lead edge of the receiver member to move in a straight line away from the dielectric member. However, due to handling constraints and core set concerns relative to the dielectric member ,there is a finite limit to the minimum diameter of the roller. Such minimum diameter may not be sufficiently small to provide the desired separation characteristics between the receiver member and the dielectric member. On the other hand, contact strippers must be carefully designed to prevent damage to the dielectric member at the contact interface. Additionally, the electrostatic forces causing adhesion of the receiver member to the dielectric member may sometimes be large enough to cause the strippers to damage the receiver member or dielectric member as they try to separate the receiver member from the dielectric member.
An example of a combined mechanical/electrical type separation device is shown in U.S. Pat. No. 3,508,824 issued Apr. 28, 1970, in the name of Lienbach et al. Such separation device employs an electrically grounded conductive plate extending from adjacent to a small diameter roller, for changing the direction of travel of a dielectric member, toward a downstream location. The change of direction of the dielectric member about the small diameter roller causes the lead edge of the receiver member to separate from the dielectric member. The receiver member is then attracted to the the grounded conductive plate, and moves along the plate to separate from the dielectric member as that portion of the receiver member still adhering to the dielectric member is moved with the dielectric member. The grounded conductive plate provides for attraction of the receiver member by assuming an electrical image charge opposite to that of the receiver member. However, depending on certain factors such as environmental conditions for example, the receiver member may not be sufficiently attracted to the conductive plate, or may be attracted to the plate with such an attractive force so as to inhibit smooth travel of the receiver member in the downstream direction.